As is known the telemark technique requires the use of ski boots which are flexible in the area of the metatarsus, since the curves are made in a "free" heel fashion, in other words with the heel raised from the ski rather than rigidly fixed to the ski fastening as in the conventional skiing technique.
Traditional telemark ski boots are made of leather, which makes it possible to obtain the necessary flexibility. In recent years the use of new generation telemark ski boots, made of plastic material, has become steadily more common, offering improved aesthetics with respect to the leather boots and greater strength and duration.
In order to allow flexibility in the area of the metatarsus, plastic boots generally have a flexible wall portion in this area. The flexibility is attained by a particular geometric configuration of the wall portion, typically corrugation or undulation, or by making this wall portion of the boot of a more flexible material with respect to the remainder of the boot. The use of plastic materials with different mechanical characteristics, in order to create parts of the boot with differing flexibility, is made possible by overinjection or co-injection.
The use of an increased flexibility area however could compromise the rigidity of the ski boot, in particular in torsion, and therefore diminish control of the skis and as a result performance and safety.